Aerofoil



June 14, 1938. HOUSTQN 2,12%,250

AEROFOIL Filed March 7, 1936 INVENTOR.

BY i 7 A TTORNEY Patna time i4, ices e'rer om Application March 7,

4 Claims.

This invention relates to aerofoil wings and in particular to wingswhich are used as lifting and sustaining surfaces for airplanes.

One of the objects of this invention is to pro- 5 duce an aeroioil wingwhich is adapted to alter the profile of the lower and upper wingsurfaces, while flying, so as to obtain a radical variation in theaerodynamical characteristics of the aerofoil.

Still another object of this invention is to provide the aerofoil framesof an airplane with a thin flexible and air tight covering which isrigidly secured to the aeroioil frame structure at the front and rearedges.

Yet another object of this invention is to provide an aerofoil wingframe with a thin, flexible and air tight envelope and in which theprofile thereof can be converted by altering the static pressure withinsaid air tight envelope, so as to maintain therein selectively either avacuum or a positive pressure.

Another object of this invention is to provide an aerofoil wingstructure with a flexible and air tight envelope which,-when theinterior as of the same is under vacuum, lies tightly against theprofile of the frame structure, and when the interior of said air tightenvelope is under positive pressure, the said envelope bulges and swellsoutwardly to a shape determined by the pres- ;0 sure against the innersurfaces and the limitations to movement imposed by its attachments atthe front and rear edges of the aerofoil frame.

Still another object of the invention is to produce an aerofoil wingwith a flexible and air tight covering. the profile of which can beselectively altered, while flying, in such a manner that the aerofoilprofile, when under vacuum, assumes the shape which approximates that ofan aeroioilgiving optimum values of high lift at low air speed, while,when the interior of the aerofoil wing is under positive pressure, theaerofoil profile approximates stream-line contour to allow maximum airspeed .to produce the sustaining lift.

Since the wing profile, when under vacuum, is a section having optimumvalues of high lift at low air speed, this permits the aeroplane to beoperated as a glider in the emergency of power failure, and vastlyincreases the range covered 50 by the gliding angle and powerlessmaneuverability, over present type of powered aeroplanes.

Yet another object of the invention is to produce an aerofoil wingprovided with a flexible covering, the profile of which is selectively55 changeable, while flying; so that by proper E936, Serial No. 6?,651

((91. Mil-44) manipulation (inflating and deflating)- deposits of ice orsuch other impediments precipitated upon the wing surfaces may be easilyloosened and detached.

Other objects of the invention will become 5 apparent as the detaileddescription proceeds.

An illustrative embodiment in diagrammatic form of the invention isrepresented by way of an example in the accompanying drawing, wherein:-

Figure l is a sectional profile view of an aerofoil wing embodying myinvention, the aerofoil envelope having a U-shaped nose or leading edgeand being shown when under internal positive pressure.

Figure 2 is a fragmentary top elevation of an aerofoil wing indiagramatic form as used in my invention, the frame structure beingpartly exposed.

Figure 3 is a sectional profile view of an aerofoil wing as shown inFigure 1 showing the flexible covering or envelope under internalvacuum.

Figure 4 is a sectional view through one of the ribs of the framestructure on line 8-4 in Figure 3.

Figure 5 is a sectional view through one of the ribs of the framestructure on line 55 in Figure 1.

Figure 6 is an enlarged fragmentary side elevation of a rounded nose onthe leading edge of the 3-3- aercfoil. I

Referring to the drawing, the aerofoii wing embodying the inventioncomprises a frame structure lt,.strong enough to not only maintain theproper acre-dynamic form of the aerofoil, but also to transmit the airpressure and lift to the body of the machine. Since it is thought thatthere is no novelty involved in the construction of the said framestructure as used in this invention, a detailed construction thereof isthere-\ fore not shown.

In general, the said frame structure comprises a series of parallellydisposed ribs Ii, curved to the aerofoil form, as shown, and usuallyjoined by crosswisely disposed spars l2. The nose H of i5 ribs H isrounded, as shown.

The aerofoil profile is of a usual type, with a concave undersurfacewhich terminates into a thinned-out trailing edge Hi, and to reduce theweight of the ribs Ii, openings l5 are provided, since lightness is aprimary consideration.

The leading edge l6 of the wing structure is provided with a U-shapednose l1 made of any suitable material, which fits over the nose I3 ofthe ribs II, and the trailing edge it may also be provided with aU-shaped nose It, or if lage as cantilevers in a usual manner (not.

shown) and care must be taken that the envelope or covering I9 maintainsits air tightness around any bracing. As additional accessories anaircompressor, a vacuum pump, valves and pipe connections are required whenusing an airplane equipped with my improved aerofoil wings.

The aforementioned accessories have not been detailed or shown for thereason that. the various features of this invention will be clear with-'out further elaboration of describing well known parts and itsconnections.

Heretofore, aerofoil wings for airplanes were generally designed tofulfill only one condition, for instance, one capable of high lift atlow air speed, or a high speed for sustaining lift, but with my improvedaerofoil wings a combination of both conditions maybe easily obtained.

The operation of an airplane embodying my invention is as follows:'

Assuming, that manually operated valves from the vacuum pump and the aircompressor are conveniently located near the pilot's seat and that apipe from the same enters the interior of each wing at the body end 20.It is suggested,

- in order to avoid too many openings in the flexible envelope orcovering I 9 'to permit only one pipe 2|, to enter each wing. This isusually done by connecting the pipes coming from the vacuum pump and thecompressor by means of a suitable fiap valve (not shown) so that asingle pipe will serve as a vacuum and compressor inlet pipe.

Before rising, the pilot opens the vacuum pump valve by means, of whichthe air in the interior of the wing] envelope will be sucked out thuscreating a vacuum within the hermetically sealed flexible envelope l9and thereby forcing the said covering to lie tightly against the framework of the aerofoil wing which then takes up a profile sectiondetermined by the design of the framework, as, for instance, illustratedin Figure 3. In this condition, the aerofoil wings are no)? adapted forhigh'lift at low air speed.

After the airplane has reached a sufiicient height, the pilot opens thecompressor valve, by means of which air is rapidly pumped into thehermetically sealed flexible envelope l9 and the same bulges and swellsoutwardly to a shape determined by the internal pressure against theinner surfaces and the limitations to movement imposed by its rigidattachments at the leading edge l6 and the trailing edge ll. of theaerofoil wing and by other attachments to the wing frame also, ifdesired. In this condition, the aerofoil wings are adaptedfor maximumair speed to produce the sustaining lift. a

When desiring to land or cruise at low speed in the air, the pilot againadjusts the aerofoil wing interior to the vacuum condition to change thewing profile to the high lift and low speed type.

As will'be'miderstood, there ma be slight changes made in theconstruction and arrange ment ofthe details of my invention withoutdeparting from the field and scope of the same and I intend to in ludeall such variations, as fall within the scope of the appended claims.

I claim:

1. An airfoil comprising an, inner supporting framework, theperimeter ofwhich is surrounded by an aerodynamical surface consisting'of=anhermetically" sealed, continuous envelope "of metal sheet,flexible due to its thinness, and partly secured to said framework, theunsecured portions of said envelope being movable in response to eithera positive or negative static pressure respectively against the innersurfaces of said hermetically sealed envelope, thus altering theaerodynamical profile of the airfoil.

2. An. airfoil comprising an inner supporting framework, the perimeterof which is surrounded by an aerodynamical surface, said surfaceconsisting of an airtight continuous envelope of metal sheet, flexibledue to its thinness and secured to the underlying framework only at theleading edge and trailing edge, the unsecured portions of said envelopebeing movable to either of two stable positions by maintainingselectively a positive or negative static pressure within said airtightcontinuous envelope, thus altering'the aerodynamical profile of theairfoil. 3. An aeronautical membercomprising an underlying framestructure, an airtight flexible continuous envelope of metal sheetsurrounding the perimeter of said member, said envelope forming theaerodynamic surfaces of said member and partly secured to said member,and means to maintain the static pressure within said airtight flexibleenvelope at either a positive or negative value with respect to theoutside atmosphere.

4..A wing for aeroplanes, comprising an underlying frame structure ofairfoil profile section,

an aerodynamic surface formed by an airtight flexible continuousenvelope of metal sheet having a perimeter substantially equal to theperimeter of the underlying frame profile section, said envelopesurrounding the perimeter of said frame structure and rigidly attachedthereto only at the leading edge and trailing edge, and means toselectively maintain either a positive or negative static pressureagainst the unsecured inner surfaces of said airtight flexible envelope.

CLAUDE M. HOUSTON.

